Bangladesh, Economic, Environmental, International, Life as it is, Technical

Our oceans: The ultimate sump

Plastic pollution

Today is “World Oceans Day,” a day observed worldwide to raise awareness about the crucial role the oceans play in sustaining life on Earth. It is also a day to appreciate the beauty of the oceans that “brings eternal joy to the soul.”

The oceans are among our biggest resources and also our biggest dumping grounds. Because they are so vast and deep, many of us believe that no matter how much garbage we dump into them, the effects would be negligible. Proponents of dumping even have a mantra: “The solution to pollution is dilution.” Really! In case they don’t know, garbage dumped into the oceans is continuously mixed by wind and waves and widely dispersed over huge surface areas.

There is a zone in the Pacific Ocean, called The Great Pacific Garbage Patch, which is a gyre of marine garbage twice the size of Texas. The garbage, mainly microplastics, were carried there by strong currents from other parts of the ocean. This is not the only floating garbage in our oceans. The Atlantic and Indian Oceans have their own garbage patches. Worse yet, the sheer size of the patches is making clean-up efforts an extremely difficult task.

Surely, human activities are impacting the oceans in drastic ways. Some of the anthropogenic environmental issues that are affecting the oceans are plastic pollution, oil spills, climate change and noise. One of the most dangerous threats the oceans may face in this century is radioactive pollution.

Each year, we dump nearly eight million tonnes of plastic—mostly grocery bags, water bottles, yogurt cups, drinking straws and plastic utensils—into the oceans. Recently, plastic has been discovered in the deepest part (11 kilometres) of the world’s oceans, Mariana Trench in the Pacific Ocean. Extremely elevated concentration of PCBs, an environment-damaging chemical banned in the 1970s, have also been found within the sediment of the trench.

While it takes hundreds of years for plastics to decompose fully, some of them break down much quicker into tiny, easy-to-swallow particles that can easily be ingested by marine species causing choking, starvation and other impairments.

Pollution of the oceans by oil spills has been one of the major concerns for a long time. The primary source of spill is offshore drilling. The process is inherently dangerous and thus, is prone to accidents. When accidents happen, and they do happen without warning, they cause massive damage to the environment—aquatic and shore—that persists for decades to come. Some oil spills happen when tankers transporting petroleum products have accidents.

If the layer of the oil is thick enough, it smothers creatures unable to move out from under it. Besides, swimming and diving birds become covered with oil, which mats their feathers, reducing their buoyancy and preventing flight. The insulative value of feathers is also lost and the birds quickly die of exposure in cold water.

The world’s largest oil spill was not an accident; it was the result of the Persian Gulf War in 1991. The second worst disaster was the spill by BP’s Deepwater Horizon offshore rig in the Gulf of Mexico in April 2010. Both incidents killed tens of thousands of birds, marine mammals, sea turtles and fish, among others.

Land and oceans together absorb slightly more than half of all the carbon dioxide emissions, with the oceans taking a greater share. When carbon dioxide dissolves in water, it forms carbonic acid. Various studies estimate that if we keep on pumping carbon dioxide into the atmosphere at the current rate, then by the year 2100, the water of the oceans could be nearly 150 percent more acidic than they are now. Such a large increase in acidity would upset the productivity and composition of many coastal ecosystems by affecting the key species at the base of the oceanic food webs. It would also reduce calcium carbonate, which is essential for building the shells and skeletons of creatures like mussels, clams, corals and oysters.

Because oceans absorb more than 90 percent of the heat that is added to the climate system, sea level is changing, albeit unevenly. It is changing unevenly as oceans do not warm uniformly across the planet, with the southern oceans warming at a faster rate. In addition, global reef systems are slowly migrating poleward as oceans around the world continue to warm.

The single most significant contribution to rising sea level is from the thermal expansion of water. Melting ice makes the second most important contribution, but only melting of land-based ice—glaciers, ice caps and ice sheets—is significant. Ice that is already floating in the water—iceberg—makes essentially no change in sea level when it melts, because the greater density of water offsets the volume of ice that is not submerged. Other factors that contribute to the rise in sea level include wind and ocean circulations, depth of the oceans, deposition of sediments by river flows and alteration of the hydrologic cycle by humans.

According to some studies, global sea level rose by about 18 cms during the last century. In the worst-case scenario, sea level could rise by two metres by the end of the year 2100. Arguably, rising sea level is among the potentially most catastrophic effects of human-caused climate change.

The oceans are no longer “The Silent World” of the famous oceanic explorer Jacques Cousteau. Today, they are being acoustically bleached by noise from seismic blasts used for offshore oil and gas exploration, marine traffic and military sonar.

Unlike plastic pollution, noise pollution does not have the visual impact that is needed to spark an outcry and force action. It is an invisible menace that is drowning out the sounds of many marine animals, including fish, use for navigation, communicating with each other, finding food, choosing mates and warning others of potential dangers.

Whales and dolphins are particularly vulnerable to noise pollution. The deafening seismic blasts and the ping of sonar are responsible for the loss of their hearing and habitat, and disruption in their mating and other vital behaviours. The disappearance of beaked whales in the Bahamas in recent years have been attributed to testing of US Navy sonar systems in the region.

From 1946 through 1993, nuclear countries used the oceans to dispose of radioactive wastes. The United States alone dumped more than 110,000 containers of nuclear material off its coasts. Russia dumped some 17,000 containers of radioactive wastes and several nuclear reactors, including some containing spent nuclear fuel.

It is highly likely that radioactive wastes would eventually leak out of the containers because of poor insulation, volcanic activity, tectonic plate movement and several other geological factors. Indeed, last month, UN Secretary General Antonio Guterres confirmed that a Cold War era concrete “coffin” filled with nuclear waste is leaking radioactive material into the Pacific Ocean. Since radiation from nuclear wastes remains active for hundreds of thousands of years, their dangerous effects will linger for a long time and will have lethal impact on marine life.

Furthermore, six nuclear submarines — 4 Russian and 2 American — lost as a result of accidents are lying at the bottom of the oceans. They represent serious threat of radioactive contamination of the oceans, too.

One of the biggest contaminations due to radiation was caused by a series of nuclear tests conducted by the USA on the sea, in the air and underwater at Bikini Atoll in the North Pacific between 1946 and 1958. The French nuclear tests carried out during 1966-1996 in French Polynesia are responsible for other cases of intense radioactive pollution of marine ecosystems.

Clearly, we are using the oceans as the ultimate sump, partly because their very immensity seems to preclude any long-term effect, and partly because they belong to no one. This cannot continue indefinitely because in order for us to survive, we have to protect the oceans. Lest we forget, life emerged from the oceans and the source of most of the oxygen we breathe are the oceans. They have been an endless source of inspiration to humankind.

Quamrul Haider is a Professor of Physics at Fordham University, New York.

Bangladesh, Economic, Environmental, International, Political, Religious

Bangladesh’s economic potential in jeopardy

Bangladesh has come a long way since the dark days of early part of liberation (1970s) when the country did not have sufficient funds to pay for diplomatic missions abroad, when the prime minister had to rely on the charity of foreign countries to have urgent medical treatment abroad, when the country did not have money to offer proper burial to the freedom fighters. Henry Kissinger, the arch opponent of Bangladesh’s liberation, branded the country as a basket-case of the world! Those were the darkest days of the Bangladesh’s history.

Now over 46 years later, Bangladesh is in much better shape economically. Although it is still the poorest of the world’s 10 most populous nations, its economy is outperforming many of those well-heeled populous nations. The Asian Development Bank, the World Bank, the UN all indicate that Bangladesh is presently steaming ahead economically. Nonetheless, they hasten to add the caveat that unless the country urgently reforms the education system and eliminate endemic corruption, the progress may be stunted.

For the time being, the economy is flourishing. As per the Global Finance Magazine report, Bangladesh has an international reserve of USD 31.8 billion (2016) and its Gross Domestic Product (GDP) is USD 246.2 billion (2016). The GDP growth is 6.9% (2017) and the GDP per capita value is USD 1508 (2017), which is somewhat higher than that of Pakistan.

At the time of liberation, Bangladesh was primarily an agricultural country. But 46 years later in 2016, the agricultural output accounts for only 15.1%, industry accounts for 28.6% and the service sector is 56.3% of the GDP. The garment industry alone accounts for 25% of the service sector and earns 80% of all exports. This rebalancing of the economy from agriculture to multi-sectors is a tremendous success for the country.

The economic benefit was not confined to rich urban population. The national wealth has been distributed to the rural population also and poverty rates have dropped. In 1991, more than 40% of the population lived in extreme poverty and now, according to the World Bank, it is less than 14%. That means that over 42 million people have been pulled out of extreme poverty.

Bangladesh has also achieved success in population control. Although Bangladesh is one of the most densely populated countries in the world, the population growth rate has been somewhat tamed. This can be gauged when it is compared with Pakistan, as shown in the following Table.

Population Growth

Country        1955      1960      1965      1970        1975      1985      1995      2005      2015

Bangladesh  2.14%   2.73%    2.98%    3.1%        1.85%    2.73%   2.25%    1.74%    1.16%
Pakistan        1.49%   2.13%    2.51%    2.7%        2.83%    3.39%   2.67%    2.13%    2.12%

The striking feature is that before the liberation, the population growth rates in the then East Pakistan was consistently higher than the national average (comprising East and West Pakistan), but after the liberation it is consistently lower than Pakistan (previously West Pakistan). The economy of the then East Pakistan was far inferior to West Pakistan’s before liberation; but after liberation it showed dramatic improvement. The conclusion that can be drawn from the Table is that as prosperity is achieved, the population growth rate declines and vice versa. In other words, the population growth rate and the economic growth rate show negative correlation.

There are, however, ominous signs for Bangladesh in the horizon of the prospect of continued growth. The Global Finance Report had clearly spelled out that unless the education system of the country is improved and corruption is reduced, the potential economic prospect may be jeopardised. Along with these two vital issues, one may add a few more issues and these are: adversarial political system, Islamic fundamentalism and, of course, perpetual traffic congestion in the capital city, Dhaka.

The education system of the country is a major cause for concern. The standards of education, particularly in the public sector, had degenerated so much that the vast majority of graduate and even post-graduate degree holders cannot even write decent sentences either in Bengali or in English. One has only to look at the comments these imbeciles make in various newspapers. The education system has been polluted by politicising it right from the primary level. The public university teachers are less interested in teaching and more so in political sycophancy, wage increases and promotions. University teachers are promoted on the basis of length of service (just like departmental clerks), not on academic excellence or quality of teaching or research. In any department of any university, more than 50% of the teaching staff are ‘professors’ (achieved due to length of service), which is a shameful situation. The proliferation of so-called ‘professors’, with little or no calibre, makes the whole system stink.

In addition, there is a very large sector of Islamic education, which was not present even in Pakistan days. There are 19,000 madrassahs with an enrolment of about 10 million children. These children will grow up as the unproductive population! The government has also established an Islamic Foundation to supervise Imams and Mullahs of 275,000 mosques (and increasing) in the country. These people are all devoted to spreading religious messages, not economic growth!

The binary political system between the Bangladesh Awami League and the BNP makes a mockery of the democratic system. When one party gets to power, its sole aim is to keep the other party out and inflict on it as much damage as possible. Alongside this objective is concentrated efforts in syphoning of state assets as quickly as possible, as in the next election this party may not be in power.

This looting of state assets is perennial. The Anti-Corruption Commission (ACC) chairman, Iqbal Mahmood, has recently said that if large scale government corruption such as in procurement, project evaluation and implementation etc. can be avoided, then the GDP growth could go up by about 2 per cent. This means that 6.9% (2017) could well be 8.9% without corruption.

Dhaka traffic

Dhaka’s traffic condition is just a nightmare. Travelling just five or six miles across the city at any time of the day can take well over two hours. How the office workers manage to attend offices day after day is a mystery. Besides spending endless unproductive hours on the road, the people are subjected to high or very high levels of toxic pollution arising from exhaust fumes of transport vehicles. No wonder the UN report persistently categorises Dhaka as one of the most unliveable cities in the world.

Corruption is endemic right across the board. Even the definition of corruption has been rejigged. A senior politician asserted that if money is not transferred from one person to another, it cannot be called corruption. So, if students are allowed to pass exams illegally or get higher grades simply due to political affiliations, it is not corruption. If people are appointed or promoted in the public services from political considerations or sycophancy, these are not corruption! No wonder, the world bodies are pointing towards corruption as the nemesis of Bangladesh’s continued progress.

Let me finish it off with a joke. Three old men – one American, one Russian and one Bangladeshi – went to God to seek answers to their burning questions.
First, the American asked, “God, when will the politicians in America work together for the good of the people?”. God replied, “25 years.” The old man started to cry that he would not live to see that day.
Next, the Russians asked God, “God, when will democracy be restored in Russia?”. God replied, “50 years”. The old Russian started to cry that his days will be well over before that day.
Finally, the Bangladeshi asked God, “God, when will Bangladesh be free from corruption?”. God then started to cry and finally said, “Not in my lifetime.”


– A. Rahman is an author and a columnist.

Bangladesh, Environmental, International, Life as it is, Technical

Was Alchemists’ dream realised in plutonium?

Glenn T. Seaborg
Glenn T Seaborg

In the history of human civilisation, no scientific discovery exploded in the face of mankind as did plutonium-239. The element was produced for the first time on March 28, 1941 at the Lawrence Berkeley Laboratory in California by a team of physicists and chemists led by Glenn T. Seaborg, the 1951 Chemistry Nobel Laureate. It was the realisation of an alchemists’ dream of large-scale transmutation, a synthetic element produced by human being.

Seaborg submitted the paper on their discovery to the journal Physical Review, but the paper was not accepted after it was assumed that plutonium may be used to build an atomic bomb. The existence of plutonium was nonetheless loudly announced to the world by the nuclear bomb dropped over Nagasaki on August 9, 1945. Thus, plutonium came into existence as a lethal weapon-grade material. Also, the discoverers of plutonium were allowed to publish their findings after the war ended.

Plutonium-239 is a highly radioactive element. A radioactive element disintegrates emitting energetic nuclear particles and radiation. The potency of a radioactive material is determined not only by the radiation it emits but also by its half-life. A radioactive material that emits alpha particle is highly hazardous, if it is inhaled or ingested. On the other hand, materials which emit penetrating x-rays and gamma rays are hazardous even at large distances as these radiations can travel large distances in air and irradiate the whole body. The time period over which the radioactive material remains hazardous is determined by its half-life. The half-life is the time period over which the activity decays to half of its original value. A radioactive material with short half-lives will become relatively harmless in a short period of time. On the other hand, a material with long half-life will remain radioactive for a long period of time. The significant parameter from hazardous point of view is the specific activity – activity in unit mass of the substance.

Plutonium has 20 isotopes – nuclei with the same number of protons but different number of neutrons. The longest-lived is plutonium-244, with a half-life of 80.8 million years. Two other isotopes with long half-life are plutonium-239, with a half-life of 24,100 years and plutonium-242, with a half-life of 374,000 years. All of the remaining isotopes have half-life that are less than 7,000 years.

All the isotopes of plutonium are primordial elements, meaning they existed (albeit in low concentrations) since the Earth was formed 4.55 billion years ago. However, since their half-life is much less than the age of the Earth, nearly all of them had decayed into lighter elements by now. Nonetheless, small traces of plutonium-239, a few parts per trillion, were found in some uranium ores, such as the natural reactor in Oklo, Gabon. In 1971, trace quantities of plutonium-244 were discovered in Precambrian-era phosphate in southern California.

Currently, most of the plutonium found in the Earth’s environment resulted from human activities, in particular, from the now banned atmospheric testing of nuclear weapons in the 1950s. It is estimated that since 1945, about 7,700 kg has been released through nuclear explosions. As there are no natural sources of plutonium, all of the plutonium presently in stock throughout the world is produced in commercial power reactors, as well as in special purpose reactors designed for weapons production.

Plutonium-239 decays by emitting alpha particles, which is the helium nucleus. External exposure to alpha particles isn’t much of a health risk. Because of their low penetration, they are stopped by the outer layer of the skin. But they are highly dangerous if inhaled. They cause damage to DNA, which, in turn, increases the risk of cancer. Plutonium-239 in the atmosphere can enter our body through body wounds. Once inside, it remains within the body for a long period of time and irradiate the body organs and tissues by the  emission of alpha particles. It is, however, eliminated from the body very slowly through excretion. It may take around 30 to 50 years for plutonium to become biologically insignificant within our body.

The adverse effects of plutonium on the environment are not that alarming. They may enter the soil and groundwater from accidental releases and improper disposal of wastes from a nuclear reactor. Soil can also become contaminated through fallout during underground nuclear weapons testing. Plants absorb plutonium, but the levels are not high enough to cause bio magnification of plutonium up the food chain, or accumulation in the bodies of animals.

Besides using it to make nuclear weapons, plutonium is used for some peaceful purposes too. Along with uranium-235 and uranium-233, plutonium-239 as well as plutonium-241 is used as fuel in reactors at commercial nuclear power plants.

Nuclear powered cardiac pacemakers use plutonium-238 batteries. They can keep the heart ticking for up to 30 years, much longer than pacemakers using lithium-iodine cell batteries which last anywhere from about five to 12 years. When one of these patients dies, the pacemaker is removed and shipped to Los Alamos National Laboratory where the plutonium is recovered. People using plutonium-powered pacemakers are still alive though.

The US space agency NASA has used this isotope of plutonium to power its space instruments–  all the way from the experiments for the Apollo lunar missions to the deep-space probes, such as the Pathfinder, Pioneer, Voyager, New Horizons and Cassini.
Today, plutonium serves as an explosive ingredient in tens of thousands of nuclear weapons in the possession of a Superpower led by a person with questionable mental stability and a rogue nation with an enigmatic and unpredictable leader. There is a high risk that these two men may unleash this weapon of mass destruction and annihilate not only each other but also the whole of mankind.

  • The writer, Quamrul Haider, is a Professor of Physics at Fordham University, New York
Bangladesh, Environmental, International, Life as it is, Political, Religious, Technical

Is human race heading towards extinction?

If we are spared the nuclear holocaust, then pollution and climate change would be responsible for our extinction

human-race-heading (2) - Copy

Since life on Earth evolved in the form of bacteria approximately 3.5 billion years ago, there had been five mass extinctions. The first one occurred 440 million years ago and the last one 65 million years ago. They had been caused by such things as climate change due to severe ice age, volcanoes, restructuring of the Earth’s crust during the formation of the super-continent Pangaea 250 million years ago, other forces of Nature and an asteroid impact.

Extinction, albeit not on a massive scale, is a natural phenomenon, a part of evolution. An examination of the evolutionary records reveals that extinction follows a pattern of species gradually becoming extinct and being replaced by newly evolved species. That’s because there is only a finite number of available niches on our planet for species to survive. Moreover, each species has a unique lifestyle not shared by any other species. As their habitat changes, their lifestyle also changes. If species cannot adapt to these changes, they become extinct. Their place is taken by species which evolves to fit the changed environment. This is known as a gradual extinction.

In the last 500 years, a short period of time on the geological scale, some 320 birds, mammals and reptiles had become extinct. The extinction of so many species over a few hundred years makes it difficult to ascribe the phenomenon to climatological, geological or astronomical events alone. It leads one to speculate that something unusual must have happened during this time frame. In particular, were these extinctions caused by humans who had and still have a greater impact on his environment? The answer is, yes.

With our entry as an ecological factor, there has been a shift from gradual extinction to abrupt, habitat-emptying extinction. We have profoundly affected the species that share the planet with us. Because of our activities, they seem to be vanishing at an unprecedanted rapid rate. This raises the question: Are we also pushing ourselves to the precipice of mass extinction?

Indeed, many scientists are predicting that we are on track for a sixth mass extinction. This time the cause won’t be global cooling or volcanic eruptions. It will be the work of a single species ‒ the Homo sapiens.

Of the many possible scenarios, nuclear conflict is the most likely one by which human civilization may become extinct in a jiffy. With the fingers of two mentally unstable men on the nuclear button, this scenario seems to be ever more likely now. After Trump’s “fire and fury” threat, the infamous Doomsday Clock was moved ahead by 30 seconds closer to midnight. The clock was created by former Manhattan Project scientists in 1947 in an effort to bring public attention to the threat of nuclear war!

If we are spared the nuclear holocaust, then pollution and climate change would be responsible for our extinction. Today, we live in a planet poisoned by toxins dumped by us. All forms of life, including human beings, are mired in a toxic swamp. The toxins are in the food we eat, the water we drink and the air we breathe. As renowned explorer and environmentalist Jacques Cousteau said: “Water and air, the two essential fluids on which all life depends, have become global garbage cans.”

We are changing the global climate by pumping about 35 billion tonnes of carbon dioxide per year into the atmosphere. According to the World Meteorological Organization, last year’s emission was 50 percent higher than the average of the past 10 years. The present concentration of carbon dioxide in the atmosphere, 403 parts per million, is the highest in recorded history.

Thus, the dangers posed by the greenhouse effect are real and scary. Global temperature is increasing, ozone layer has been depleted, hydrological cycle is being disrupted, sea levels are rising, polar ice caps are melting, tropical rainforests are disappearing, wildfires are on the rise, semiarid lands are turning to deserts and bizarre, violent weather patterns have grown in numbers in recent years. The utter devastation of Houston, many Eastern Caribbean Islands and Puerto Rico by relentless rains, punishing winds and dangerous storm surges caused by hurricanes Harvey, Irma and Maria in August and September of this year are still fresh in our memory.

What is more alarming is that if we allow our planet to become even warmer, then hundreds of millions of tonnes of frozen methane buried under the Arctic Ocean floor, often referred to as the “Arctic Time Bomb,” would be released into the atmosphere. In an article published in 2014 in the journal Science, researchers report that concentration of methane in the atmosphere has been growing rapidly since 2007. They believe that due to rising temperatures across the entire Arctic region, which are already melting the Siberian permafrost, the trapped methane is being released into the atmosphere.

In addition to methane, carbon dioxide in the rocks would be “baked out” and ocean water would evaporate into the atmosphere. Water vapor and methane are more cogent greenhouse gases than carbon dioxide. The increase of atmospheric carbon dioxide, methane and water vapor would raise the global temperature further, thereby causing more ocean evaporation, baking out of carbon dioxide and release of methane. The synergistic feedback of continued emission of these and other greenhouse gases could trigger the onset of runaway greenhouse effect which will eventually turn the Earth into an inferno with virtually no life.

Runaway greenhouse effect is not a “Chinese hoax.” Several billion years ago, Venus was cooler than what it is now and had abundance of water in oceans overlain by an oxygen-rich atmosphere. The current hellish condition on Venus where the surface temperature is a blistering 460 degrees Celsius was caused by runaway greenhouse effect.

A rapidly growing human population that more than doubled in just the last fifty years is also putting us on the throes of extinction. With a burgeoning population, food, water and a whole lot more required for sustenance of life will be in short supply. Natural resources vital to our survival are already running out faster than we can replace them with sustainable alternatives. In some cases, they have already reached their limits. Hence, it is not unlikely that once the population reaches a “critical mass,” our resources won’t be adequate enough to sustain us. As a result, starvation will bring us face-to-face with extinction, sooner rather than later.

Finally, we cannot rule out the possibility of a fast-spreading devastating disease that could wipe us out. Furthermore, with the advancement in DNA manipulation technology, it is quite likely that scientists working for the leader of a rogue nation could engineer a vicious virus or bacteria for a biological warfare and in the process obliterate our entire civilization.

For most part of the evolutionary past, we lived in a sustainable relationship with Nature, not necessarily out of choice but out of necessity. But in the past few centuries, we have gone astray. Now, we are living at odds with the natural world. We seemed to have lost touch with the magnitude of our effect on the environment. In fact, we have become a super predator pushing other species that call this planet home toward extinction.


As for ourselves, by letting population grow exponentially, burning fossil fuels unchecked, polluting the environment with toxins and facing the threat of extermination with weapons of mass destruction, we have embarked on the path to self-annihilation. Such a human race cannot survive for long unless dramatic changes are made to create a sustainable future.

Barring a nuclear armageddon, we may not witness the sixth mass extinction during our lifetime. However, one hundred years or so from now, more of human-caused stress on our planet could accelerate the occurrence of the sixth and perhaps the last mass extinction.

The writer, Quamrul Haider, is a Professor of Physics at Fordham University, New York


Bangladesh, Environmental, International, Political

Noise Pollution – Plague of the Modern Society


Perennially chaotic Dhaka streets

Sound is one of many forms of expression and a very important aspect of human life. It can, however, be pleasant or unpleasant. Whether sound is as pleasant as music or as unpleasant as noise depends on its intensity, duration, rhythm and mood of the person. But when intensity goes beyond what is pleasant, it becomes a problem, and hence, a pollutant.

Noise pollution is a plague of modern society from which there is virtually no escape, no matter where we are – in our homes or gardens, on our streets, inside our cars, at theatres or concerts, social events, restaurants, parks or in other public places. Like second-hand smoke, noise has become an unwanted airborne pollutant produced by others and imposed on us without our consent, often against our will.

The unit used to gauge the loudness or sound intensity is decibel (dB). Decibel is one-tenth of a bel (B). The bel (B) measures the ratio of one intensity or power of sound to the intensity or power of the reference sound in a logarithmic scale (log to the base of 10). After that, bel is converted to dB scale by multiplying by 10. The reference level of sound intensity is 1 and hence its dB value is 0, which is taken as the threshold of hearing. A sound 10 times as loud as the reference level has a dB value of 10. A 20 dB is 100 times as loud as the threshold of hearing, 30 dB is 1000 times, and so on. The maximum loudness humans can be subjected to, after which sound can be felt rather than heard, is approximately 120 dB. This is known as the threshold of pain.

Among the many sources of outdoor noise pollution, automobiles are the worst offenders in the western world, followed closely by trucks, buses, motorcycles and low-flying airplanes. Construction equipment, such as jackhammers, compressors and bulldozers, also contribute substantially to noise pollution. Noise levels of these sources range from 50 dB to 120 dB. But in Bangladesh, high dB speakers at the top of mosques are the worst offenders. In some residential places close to the mosques, noise levels exceed 120 dB or 130 dB quite regularly.

Those living within 600 metres of an airport are exposed to 100-120 dB of noise from jet planes taking off. At 1,500 metres away, the level drops to 80 dB. A car cruising at 100 kmph, 80 metres from the pavement’s edge would produce 75 dB. Because of the logarithmic nature of decibel, adding sound intensity from two cars would increase the level by 3 dB; three cars would augment the level by 4.8, and so on.

Some household appliances, such as dishwasher, food blender, air conditioner and vacuum cleaner, are annoyingly loud – 70 to 100 dB. Depending on the distance from the source, sound from living room audio and video systems could be near 80 dB.

In Dhaka, irrespective of where you live, the noise intensity level is very close to the threshold of pain. Most of it is due to the religious cacophony and noise produced by the horns of vehicles plying on the roads, highways, byways and lanes of the city. Although noise is a controllable pollution, government of Bangladesh has done very little to alleviate the suffering of its citizens from this pestilence.

Hearing damage from loud noise depends on the decibel level, length of exposure and distance from the source. According to the US Occupational Safety and Health Administration, if you are exposed to 95 dB and above for four hours a day over a long period, you will slowly start to lose your hearing ability. As the damage from noise exposure is usually gradual, you might not notice hearing loss until it becomes acute.

Damage from loud noise can be temporary or permanent, depending on whether the organs of Corti, the receptor organs in the inner ear, are impaired or destroyed. In the extreme case, exposure to 150 dB would rupture the eardrum. Less intense, but severe noise can interfere with cellular processes in the organs that cause their eventual breakdown. Unfortunately, the cells of these organs do not regenerate.

Generally, younger persons are more tolerant of loud noise than older persons because their protective mechanisms are more effective. This tolerance does not necessarily make them immune to adverse effects from loud noise. For example, blood tests done on children living near airports in Munich, Germany reveal significantly higher levels of adrenaline and cortisol – the body’s stress hormones, than children living in quieter neighbourhoods. The increase in cortisol adds to the risk of having a heart attack or stroke later in life. Similar impacts have been documented among adults near Amsterdam’s Schiphol and Stockholm’s Arlanda airports, where chronic noise as low as 55 dB correlated with more doctor visits, high blood pressure and treatments for heart troubles.

And what about the sound of music? The line that separates music and noise is thin and subjective. While to some people noise may not be an issue, others consider contemporary music and music from other cultures to be noise pollution. Take heavy-metal and rap, for example. They are considered to be music by many people, though most of the songs cannot be transcribed into notes and some of them don’t even have melody.

Is hearing permanently impaired when attending concerts that feature very loud music? Yes, they are because typical sound intensity level of a loud rock concert is near the threshold of pain. Of course, the extent of impairment will depend on how long you are exposed to the noise and how often you attend such concerts. That’s why many musicians and DJs wear earmuffs to protect their hearing organ from the harmful effects of noise. A drop of 30 dB corresponds to a decrease in intensity (not intensity level) by a factor of 1000.

A growing body of evidence confirms that noise pollution is taking a toll on our health and happiness, too. Studies have linked excessive noise levels to the occurrence of aggressive behaviour, constant stress, fatigue and hypertension. These in turn can cause more severe and chronic health issues later in life. Repeated exposure to noise also reduces sleeping hours, thereby, decreasing the productivity of a person.

According to a World Health Organisation (WHO) report to the UN Conference on Environment, “Of all environmental problems, noise is the easiest to control.” However, the question of control will arise only after we become aware of the seriousness of the problem, and the government finds some solution for it.

The writer is a Professor of Physics at Fordham University, New York.